The narcissists in fandom believe that everything - literally everything - is about them and that they are the Arbiters of All Good Taste. If they don't like something, no one can like it. If they like something, everybody has to like it. They post their preferences, ideas, and opinions in every public forum possible without bothering to a) consider other people's thoughts, b) filter or modulate themselves in any regard , or c) understand that the world doesn't actually need them to broadcast their every inane passing thought. They lack any sort of empathy and any willingness to understand anyone's else perspectives or feelings.
How To Deal With It: Don't bother arguing or protesting. Narcissists aren't interested in reasonable debate; they're just interested in being right and in gathering an audience for their opinions. They will make it all about them. Block, block, block or avoid, avoid, avoid.
No matter how fast a sub comes out, it's never fast enough. No matter how hard translators work on a chapter, it's never soon enough. No matter how little time a game spends in beta testing, it is too damn long and they're tired of waiting. Greedy fans complain about everything: they want it all and they want it now. They fill fandom tags with irritable and/or repetitious comments: "When is this coming out already?" They criticize translators and companies for not moving at their pace. Fandom exists to satisfy their every urge, and when they aren't happy, nobody's happy.
How To Deal With It: If you sense genuine ignorance, inform them respectfully that x chapter comes out on x day and that is the way it has always been since the dawn of time and the rising of the phoenix from the first age. If they still complain, block them. Or distract them with a shiny new series so that they have 173 chapters to catch up on before they start complaining again.
"lmaoooo I just read like one chapter of this can someone explain the last seventy chapters to me tho"
"So is [Major Character Who Is Totally A Bad Guy?] a bad guy? I didn't read but I really want to know?"
People who commit the sin of sloth aren't usually malicious, mean, or ill-intentioned. Sometimes they're lazy, sometimes just eager, and sometimes confused. They come to a fandom they find interesting and, rather than doing the dig work on their own or looking up that joke or checking a tag to make sure the same thing hasn't been referenced 9,999 times already, they ignore context and do whatever the hell they feel like doing. This is a forgivable sin, but it can really, really irritate old hats in the fandom.
How To Deal With It: If you suspect genuine ignorance or a newbie to the fandom, be respectful and kind. Encourage them to check the tags; refer them to wikis and informational posts. If they're just being lazy and want fandom to do the easy work they refuse to do, ignore it. They'll get tired of asking eventually.
You know these people. They post provocative things just to set the fandom on fire; they make nasty personal attacks. They spam the tags with inflammatory "COME AT ME" posts and consider it their job to bring everybody down a peg or two or a thousand. They can't be reasoned with and they're not around to enjoy fandom so much as they are to destroy it or to just enjoy the endless conflict.
How To Deal With It: Whatever you do, don't engage. It only adds fuel to the fire and you risk making yourself a target. Assume "troll" if need be, then roll your eyes and figuratively walk on by. If necessary, take advantage of whatever abuse-reporting practices you have available to you.
I differentiate boorishness from malice because boorishness usually stems from carelessness rather than from negative feelings or a desire to provoke conflict. Boorishness is simply rudeness: all the myriad improprieties perpetrated by those in fandom.
Boorish fans post nsfw or triggering work to public forums and don't bother to tag it. They reply publicly to private messages on purpose. They send things like "ARE YOU EVER GOING TO WRITE THAT ANALYSIS NOW GOD HURRY" without realizing it makes them sound like an asshole. They write carelessly cruel things in the tags about the art and fic they reblog. They don't bother to measure or qualify their opinions or posts. Boorish people just generally don't give a shit about doing anything other than what they want to do, and if that bothers you, well...they don't hate you and they're not trying to offend anybody, but they really don't care.
How To Deal With It: Asking them to stop probably won't change their behavior. If they irritate you, leave them to their own little corner of fandom and blacklist/ignore/avoid them if need be.
They routinely post others' fanart, fanfic, and edits without attribution. Occasionally, they'll claim it as their own. You can identify by them by the copious amounts of half-assed "CREDIT TO THE AUTHOR" and Zerochan/weheartit "sources" all over their posts. If you're having a really bad day, you'll find them to be the "authors" of that cool .gif you just posted - that they stole, erased the watermark on, and then reposted as their own.
How To Deal With It: Message them and respectfully inform them of the problem and ask them to correct it. If they don't, report the plagiarism/art theft if possible. If not, reblog or repost their material and add the source conspicuously beneath. Occasionally this sort of public shaming will suffice.
Those overwhelmed with pride are most often the veterans - the people who, by virtue of being in a fandom for eternity, consider themselves an expert on it and think that anyone who knows less than they do (or whom they perceive knows less than they do) has nothing of value to offer. They will correct every minor mistake they find in someone else's fandom post; they will fight to the bloody death over their headcanons. Anything that dares to contradict their ideas and expertise about the series is considered an offense, and they often set themselves up as the Gods of Their Fandom: all-knowing beings who crush any usurpers and take a special pleasure in treating new members of a fandom like shit. Periodically, those overcome with pride will attack anyone who dares critique or analyze their series with anything less than 100% positivity, and you will know them by the tone of their posts and communications, which carry a curated mix of disdain, arrogance, and weariness.
How To Deal With It: Laugh at them and keep on posting your stuff. Oh, and if you're going to engage them in a debate, be sure to know your shit or they will rip you apart.